Bearing assembly method and pressurization jig

ABSTRACT

According to one embodiment, a bearing assembly method for providing a bearing between a shaft and a rotator, comprises: embedding the bearing between the shaft and the rotator, and supplying a first adhesive between an inner ring of the bearing and the shaft and a second adhesive between an outer ring of the bearing and the rotator; partially pressing a plurality of points on an end surface of the inner ring before the first adhesive and the second adhesive are cured; and finishing pressing when the first adhesive and the second adhesive are cured.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT international application Ser. No. PCT/JP2007/072277 filed on Nov. 16, 2007 which designates the United States, incorporated herein by reference.

BACKGROUND

1. Field

One embodiment of the invention relates to a bearing assembly method and to a pressurization jig.

2. Description of the Related Art

In the process of manufacturing a magnetic disk device, it is required to perform a performance test before embedding a magnetic head in a product. The performance test of the magnetic head is performed by attaching a number of magnetic heads to one actuator block for testing a number of magnetic heads, for example, 40 magnetic heads, at once. In the performance test, it is required to swing the actuator block such that movement of the magnetic head is the same as the movement of a magnetic head in an actual product. That is, it is required to make distance from the center of swing of the actuator block to the attached magnetic head equal to distance from that of the actuator to the magnetic head in an actual product (magnetic disk device).

The actuator block of a testing device is formed to be swingable around a shaft using a ball bearing. Since a number of magnetic heads are attached to the testing device, the swinging mechanism needs to be more rigid and durable than the actual product. Therefore, the bearing used between the actuator block and the shaft is required to be larger than the bearing in the actual product.

As described above, it is not possible to use a unit bearing (integration of the shaft, a collar, and the bearing) attached to the actual product in the actuator block in the testing device, and the large bearing is often directly attached to the shaft. That is, the actuator block capable of supporting a number of magnetic heads is prepared, and the shaft and the bearing are attached to the actuator block.

Although there is no conventional technology of the method of attaching the bearing to the actuator block as described above, there has been proposed a method of fixing the bearing by deforming an end of the shaft mounted with the bearing as a method of attaching the bearing to a motor shaft (for example, see Japanese Patent Application Publication (KOKAI) No. 2005-180583).

In the process of attaching the shaft and the bearing to the actuator block, the shaft is inserted into a through-hole of the actuator block, and ball bearings are attached near both ends of the through-hole. With this, the actuator block becomes swingable relative to the shaft. It is required to make swing action of the actuator block extremely smooth, the ball bearing and the shaft as well as the ball bearing and the actuator block are often fixed not by press fit or the like but with an adhesive.

To fix the ball bearing with the adhesive, it is necessary to press the ball bearing against the actuator block by applying a pressing force thereto until the adhesive is cured to position the ball bearing with high accuracy. In general, an end surface in the axial direction of an outer ring of the ball bearing is supported by a surface of a housing of the actuator block, and an inner ring of the ball bearing is pressed in the axial direction to fix the ball bearing at a predetermined position until the adhesive is cured.

In general, by pressing the ball bearing in the axial direction, a jig is pressed against the entire end surface of the inner ring or the outer ring of the ball bearing to uniformly press the entire end surface. However, since extremely smooth action is needed in the actuator block for swing of the magnetic head, for example, when the entire surface of the inner ring of the ball bearing is pressed, a portion at which swing (rotation) is not smooth, a “stuck” and “gritty feel”, may be caused. This may occur because the inner ring is pressed against balls in the ball bearing and slightly deforms when the inner ring is pressurized, so that uniform load does not act on each ball. That is, as one of causes may be cited that the inner ring or the outer ring cannot elastically deform at a portion at which a specific ball is located due to an error in dimension of the ball, the inner ring, and the outer ring, and slightly plastically deform. If such deformation occurs, during the rotation of the actuator block, friction temporarily becomes large when the specific ball moves to a deformed portion, and the “stuck” and “gritty feel” occur. When the actuator block is used in the state where there is the “stuck” and “gritty feel”, since a swing movement amount of the actuator block is controlled by torque, desired swing may not be achieved.

Actually, it is difficult to detect nonsmooth rotation such as the “stuck” and “gritty feel” by a machine. Therefore, an assembling worker manually rotates the actuator block to detect a slight “stuck” by fell. This detection work requires a considerable time and can be performed only by a skilled worker, and thus is troubling and requires more costs.

Besides, since the actuator block in which the “stuck” and “gritty feel” are generated cannot be used, for example, there is a case where the assembled ball bearing and the shaft are once detached from the actuator block, cleaned and assembled again. This requires time and labor.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.

FIG. 1 is an exemplary exploded perspective view of an actuator block assembled by a bearing assembly method according to an embodiment of the invention;

FIG. 2 is an exemplary perspective view of the state where a shaft and a bearing are assembled to the actuator block illustrated in FIG. 1 in the embodiment;

FIG. 3 is an exemplary enlarged cross-sectional view of a portion in which the bearing is embedded in the embodiment;

FIG. 4 is an exemplary perspective view of a pressurization jig viewed from a side contacting the bearing in the embodiment;

FIG. 5 is an exemplary perspective view of the pressurization jig viewed from a side opposite the side contacting the bearing in the embodiment; and

FIGS. 6A, 6B, 7A, and 7B are exemplary views illustrating the positional relationship between balls in the bearing and the bearing pressing surfaces of the pressurization jig in the embodiment.

DETAILED DESCRIPTION

Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, there is provided a bearing assembly method for providing a bearing between a shaft and a rotator. The bearing assembly method comprises: embedding the bearing between the shaft and the rotator, and supplying a first adhesive between an inner ring of the bearing and the shaft and a second adhesive between an outer ring of the bearing and the rotator; partially pressing a plurality of points on an end surface of the inner ring before the first adhesive and the second adhesive are cured; and finishing pressing when the first adhesive and the second adhesive are cured.

According to another embodiment of the invention, a pressurization jig configured to apply a pressing force to a bearing upon assembly of the bearing comprises bearing pressing surfaces configured to partially press an end surface of the bearing at a plurality of points.

An actuator block 10 assembled by a bearing assembly method according to one embodiment is described with reference to FIGS. 1 and 2. FIG. 1 is an exploded perspective view of the actuator block assembled by the bearing assembly method according to the embodiment. FIG. 2 is a perspective view of the state where a shaft and a bearing are assembled to the actuator block 10.

The actuator block 10 illustrated in FIG. 1 is a rotator, which rotates or swings while supporting a number of magnetic heads for performing a performance test of the magnetic heads. Since swing action the same as that of the actuator in an actual magnetic disk device is required, the actuator block 10 needs to be smoothly rotatable.

A through-hole 10 a is provided on the actuator block 10 in the longitudinal direction thereof, and a shaft 12 is inserted into the through-hole 10 a. Ball bearings 14-1 and 14-2 are attached to both ends of the through-hole 10 a. Therefore, the actuator block 10 is rotatable or swingable around the shaft 12 while being supported by the bearings 14-1 and 14-2.

FIG. 1 illustrates the state where the shaft 12 is partially drawn out downward and the bearings 14-1 and 14-2 are detached from the actuator block 10. A pressurization jig 20, described later, is illustrated above the upper bearing 14-1.

A state in the process of embedding the shaft 12 and the bearings 14-1 and 14-2 in the actuator block 10 is illustrated in FIG. 2. The shaft 12 and the bearings 14-1 and 14-2 are placed in the through-hole 10 a of the actuator block 10, and the bearings 14-1 and 14-2 and the actuator block 10 and the shaft 12 are fixed to each other with an adhesive. With this, the actuator block 10 becomes rotatable through the bearings 14-1 and 14-2.

The lower bearing 14-2 is forced into the through-hole 10 a of the actuator block 10 by being pressed by a protrusion provided on the lower end of the shaft 12. Therefore, in the state where the shaft 12 is placed in the through-hole 10 a, the position of the lower bearing 14-2 is fixed in the state of being forced into the through-hole 10 a.

On the other hand, a pressing force in the axial direction is not applied to the upper bearing 14-1 in the state of being placed in the through-hole 10 a. Therefore, it is necessary to apply a pressing force to the upper bearing 14-1 to hold it at a predetermined position in the through-hole 10 a until the adhesive to fix the bearing 14-1 is cured. Then, in the embodiment, the pressing force is applied to the bearing 14-1 by using the pressurization jig 20 until the adhesive is cured to hold the bearing 14-1 at the predetermined position in the through-hole 10 a.

Next, pressurization of the bearing 14-1 by the pressurization jig 20 is described with reference to FIGS. 3 to 5. FIG. 3 is an enlarged cross-sectional view of a portion in which the bearing 14-1 is embedded. FIG. 4 is a perspective view of the pressurization jig 20 viewed from a side contacting the bearing 14-1. FIG. 5 is a perspective view of the pressurization jig 20 viewed from a side opposite the side contacting the bearing 14-1.

As illustrated in FIG. 3, a large diameter portion is provided on the upper end of the through-hole 10 a of the actuator block 10 and the bearing 14-1 is placed in the large diameter portion. A step is provided on a bottom surface of the large diameter portion such that an end surface of an outer ring 14-1 a of the bearing 14-1 abuts on the bottom surface and an inner ring 14-1 b of the bearing 14-1 does not abut on the bottom surface of the large diameter portion. A plurality of balls 14-1 c are arranged between the outer ring 14-1 a and the inner ring 14-1 b of the bearing 14-1 such that the outer ring 14-1 a and the inner ring 14-1 b are rotatable relative to each other.

A small groove is formed on a portion of the shaft 12 contacted by the inner ring 14-1 b, and an adhesive 22-1 is supplied to the groove. The adhesive 22-1 is supplied to the groove of the shaft 12 in advance and the adhesive 22-1 is configured to spread between the shaft 12 and the inner ring 14-1 b when the bearing 14-1 is assembled to the shaft 12. A groove is also formed on an inner wall of the large diameter portion of the through-hole 10 a and an adhesive 22-2 is supplied to the groove. The adhesive 22-2 is configured to spread between the inner wall of the larger diameter portion and the outer ring 14-1 a when the bearing 14-1 is assembled to the large diameter portion of the through-hole 10 a of the actuator block 10. Meanwhile, a lateral hole 10 b is connected to the groove formed on the inner wall of the large diameter portion from an outer surface of the actuator block 10. After storing the bearing 14-1 in the large diameter portion of the through-hole 10 a of the actuator block 10, the adhesive 22-2 may be supplied from outside to the groove through the lateral hole 10 b.

As for the lower bearing 14-2 also, the adhesive is similarly supplied to fix the same.

As described above, by embedding the shaft 12 and the bearings 14-1 and 14-2 in the through-hole 10 a of the actuator block 10 to cure the adhesives 22-1 and 22-2, the actuator block 10 becomes rotatably supported by the shaft 12 through the bearings 14-1 and 14-2. It is required that the outer ring 14-1 a of the bearing 14-1 abuts on the bottom surface of the large diameter portion of the through-hole 10 a when curing the adhesives 22-1 and 22-2. Therefore, it is required to apply the pressing force to the bearing 14-1 until the adhesives 22-1 and 22-2 are cured. Then, by applying pressure to the inner ring 14-1 b of the bearing 14-1 by the pressurization jig 20 until the adhesives 22-1 and 22-2 are cured, the bearing 14-1 is pressed against the bottom surface of the large diameter portion of the through-hole 10 a.

The pressurization jig 20 is a thin cylindrical member formed of metal, ceramics, and the like having high rigidity and is configured such that the inner through-hole 10 a fits an outer diameter of the shaft 12. The pressurization jig 20 has convex portions 24 on each of which a bearing pressing surface 24 a is formed on a lower surface side thereof as illustrated in FIG. 4 and has convex portions 26 on each of which a pressed surface 26 a is formed on an upper surface side thereof as illustrated in FIG. 5.

The convex portions 24 are arranged at regular intervals along an end surface of the inner ring 14-1 b of the bearing 14-1. Three convex portions 24 are provided in the embodiment and adjacent convex portions 24 are in a positional relationship of 120 degrees therebetween. On the other hand, the convex portions 26 are also provided on three points and adjacent convex portions 26 are in a positional relationship of 120 degrees therebetween. Each convex portion 26 on the upper surface side is arranged to be in the middle of the adjacent convex portions 24 on the lower surface side.

By arranging the pressurization jig 20 on the bearing 14-1 along the shaft 12 after inserting the shaft 12 into the through-hole 10 a of the actuator block 10 and storing the bearing 14-1 in the large diameter portion of the through-hole 10 a, a state as illustrated in FIG. 3 is obtained. In this state, the bearing pressing surfaces 24 a of the three convex portions 24 abut on the end surface of the inner ring 14-1 b of the bearing 14-1. Since the convex portions 24 are provided at an interval of 120 degrees, only one convex portion 24 is represented as a cross-section in FIG. 3.

In the state illustrated in FIG. 3, until the adhesives 22-1 and 22-2 are cured, equivalent pressing force is applied to the convex portions 26 of the pressurization jig 20. With this, three points of the inner ring 14-1 b of the bearing 14-1 are pressed at regular intervals. As a result, the outer ring 14-1 a is pressed against the bottom surface of the large diameter portion of the through-hole 10 a and the bearing 14-1 is held at the predetermined position. When curing of the adhesives 22-1 and 22-2 is completed, pressurization by the pressurization jig 20 is released and the pressurization jig 20 is detached from the shaft 12. Since the adhesives 22-1 and 22-2 are cured, the inner ring 14-1 b of the bearing 14-1 is fixed to the shaft 12 and the outer ring 14-1 a of the bearing 14-1 is fixed to an inner surface of the large diameter portion of the through-hole 10 a of the actuator block 10. Therefore, the actuator block 10 is rotatably or swingably attached to the shaft 12 through the bearing 14-1 (and the bearing 14-2).

As described above, by applying the pressing force only to the three points of the inner ring 14-1 b of the bearing 14-1 by the three convex portions 24 of the pressurization jig 20, probability of pressurizing the portions of the inner ring 14-1 b contacted by the balls 14-1 c in the bearing 14-1 may be minimized. For example, when an entire end surface of the inner ring 14-1 b is pressed as in a conventional manner, the pressing force is applied to all the portions contacted by the balls 14-1 c of the inner ring 14-1 b, and probability that a portion at which rotation is not smooth is generated, i.e., probability that “stuck” and “gritty feel” are generated due to increasing friction becomes high. By applying the pressing force not to the portion contacted by the balls 14-1 c of the inner ring 14-1 b but to a portion between the adjacent balls 14-1 c, the inner ring 14-1 b may slightly elastically deform without being disturbed by the balls 14-1 c, so that possibility that the “stuck” and “gritty feel” are generated may be reduced. However, since the balls 14-1 c rotate in the bearing 14-1, it is not possible to know the positions thereof.

Therefore, it is effective to reduce the possibility that the “stuck” and “gritty feel” are generated by reducing the probability that the portions contacted by the balls 14-1 c of the inner ring 14-1 b are pressurized as far as possible. That is, by reducing the number of the convex portions 24 each having the bearing pressing surface 24 a as far as possible, the probability that the portions contacted by the balls 14-1 c of the inner ring 14-1 b are pressurized may be reduced as far as possible.

In the embodiment, as illustrated in FIG. 6, the three convex portions 24 are arranged at regular intervals. It is not preferable to arrange one convex portion 24 because this cannot flatly pressurize the entire inner ring 14-1 b of the bearing 14-1. When the two convex portions 24 are arranged in a diameter direction, the pressing force may act orthogonally to the inner ring 14-1 b of the bearing 14-1. By arranging the three convex portions 24 at regular intervals as in the embodiment, the entire inner ring 14-1 b may be flatly pressurized. That is, the minimum number of the convex portions 24 is three and it is most preferable to set the number of the convex portions 24 three to reduce the number of the convex portions 24 as far as possible. As illustrated in FIGS. 6A and 6B, when arranging the convex portions 24 at regular intervals by making width of the bearing pressing surface 24 a thereof equivalent to a diameter of the ball 14-1 c, the probability of pressurizing the portions contacted by the balls 14-1 c becomes one-tenth of that when the entire end surface of the inner ring 14-1 b of the bearing 14-1 is pressurized when the balls 14-1 c are on the positions illustrated in FIG. 6A and the positions illustrated in FIG. 6B. That is, although the convex portion 24 conforms to a contact portion of only one (a blacked out ball) of the ten balls 14-1 c in FIGS. 6A and 6B, when pressurizing the entire end surface of the inner ring 14-1 b, this is equivalent to the case where the convex portion 24 conforms to all the contact portions of the ten balls 14-1 c, so that the probability that the convex portion 24 conforms to the contact portion of the ball 14-1 c is one out of ten, or equivalently, one-tenth.

If the length of the bearing pressing surface 24 a of each convex portion 24 (i.e., length in the circumferential direction of the convex portion 24) is larger, as illustrated in FIG. 7A, the probability that the convex portion 24 conforms to the contact portion of the ball 14-1 c increases. FIGS. 7A and 7B are views illustrating the case where the width of the bearing pressing surface 24 a in FIGS. 6A and 6B is made twice. Although the convex portion 24 conforms to only one ball 14-1 c in FIG. 7B, when a position of the pressurization jig 20 slightly rotates as illustrated in FIG. 7A (i.e., when the convex portion 24 rotates), the convex portion 24 conforms to two balls 14-1 c.

As described above, although the width of each bearing pressing surface 24 a is preferably smaller, when this is too small, the pressing force is concentrated and the pressing force per unit area increases, so that the inner ring 14-1 b of the bearing 14-1 easily deforms. Therefore, it is preferable that the length of each bearing pressing surface 24 a be not larger than the diameter of the ball 14-1 c and the width thereof is such that the pressing force per unit area is not too large.

As described above, the bearing pressing surfaces 24 a are provided on three points of the pressurization jig 20 and pressurizing surfaces 24 b also are provided on three points to be in the middle of the bearing pressing surfaces 24 a in the embodiment. By providing the pressurizing surfaces 24 b in the middle of the bearing pressing surfaces 24 a, it is possible to disperse the pressing force applied to the pressed surfaces 26 a to transmit to the bearing pressing surface 24 a, thereby equalizing the pressing force.

The pressurization jig 20 is preferably thicker to prevent deformation, and it is preferable that deflection be little when the pressing force is applied to the pressed surface 26 a. Since magnitude of the pressing force differs according to the type of the bearing 14-1, grease filled in the bearing 14-1, and the like, although it cannot be said unconditionally, when the inner diameter of the bearing pressing surface 24 a of the pressurization jig 20 is 5 to 6 mm and a total of 2 kgf pressing force is applied to the entire pressed surfaces 26 a, for example, it is preferable to determine the thickness such that the deflection of the pressurization jig 20 is not larger than 1 μm. In this case, when the pressurization jig 20 is formed of metal, the pressurization jig 20 having the thickness of approximately 4 mm satisfies a condition that the deflection is not larger than 1 μm. It is preferable that the thickness of the pressurization jig 20 be determined based on a material of the pressurization jig 20, the type of the bearing 14-1 and a type and an amount of the grease filled in the bearing 14-1.

As described above, according to the embodiment, it is possible to prevent ununiformity of the friction at the time of rotation of the rotator generated due to embedding of the bearing 14-1 when embedding the shaft in the actuator block 10 through the bearings 14-1 and 14-2. Therefore, the actuator block 10 can smoothly rotate relative to the shaft 12 and accuracy of the rotational position of the actuator block 10 can be increased.

While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 

1. A bearing assembly method for providing a bearing between a shaft and a rotator, the bearing assembly method comprising: embedding the bearing between the shaft and the rotator, and supplying a first adhesive between an inner ring of the bearing and the shaft and a second adhesive between an outer ring of the bearing and the rotator; partially pressing a plurality of points on an end surface of the inner ring before the first adhesive and the second adhesive are cured; and finishing pressing when the first adhesive and the second adhesive are cured.
 2. The bearing assembly method of claim 1, wherein the partially pressing comprises pressing the inner ring with a pressurization jig comprising bearing pressing surfaces arranged at regular intervals along the end surface of the inner ring.
 3. The bearing assembly method of claim 2, wherein a pressing force is applied to the pressurization jig at a portion in a middle of each bearing pressing surface.
 4. The bearing assembly method of claim 2, wherein the bearing pressing surfaces are three bearing pressing surfaces arranged at regular intervals along the end surface of the inner ring, and a length of each bearing pressing surface along the end surface of the inner ring is equal to or less than a diameter of a ball of the bearing.
 5. The bearing assembly method of claim 1, wherein the rotator is a rotary actuator block of a magnetic disk device, the shaft is assembled to extend through the rotary actuator block, and the bearing is attached on an end of the shaft with the first adhesive and the second adhesive.
 6. A pressurization jig configured to apply a pressing force to a bearing upon assembly of the bearing, the pressurization jig comprising: bearing pressing surfaces configured to press an end surface of the bearing at a plurality of points.
 7. The pressurization jig of claim 6, wherein the bearing pressing surfaces are arranged at regular intervals in a circumferential direction.
 8. The pressurization jig of claim 7, further comprising a pressed surface to which the pressing force is applied from the outside in a middle of an adjacent pair of the bearing pressing surfaces.
 9. The pressurization jig of claim 6, wherein the bearing pressing surfaces are provided on three points at regular intervals along an end surface of an inner ring of the bearing, and a length of each bearing pressing surface along the end surface of the inner ring is equal to or less than a diameter of a ball of the bearing. 